This 'appropriate metaphor' becomes the name of the geth platform Commander Shepard found on the derelict Reaper.
For people who don't know Mass Effect, geth are Artificial Intelligences who turned against their creators since they claimed to have a soul and ask themselves questions about their existence, i.e. mechanical slaves designed to achieve dangerous and/or repetitive tasks.
The appaerance of consciousness amongst machines remains an unanswered question and leads to philisophical and ethical questions...
Every geth platform is connected with the rest of them, that is why Legion refers to himmself as 'we'.

This unit has military and technical skills, such as building simple drones, recharging shields, hacking simple IA structures...It wears a piece of human armor, probably as quick repair parts, and the hull on the trunk is damaged (thus the asymetry of the Lego model).

Here are more details and pictures about the original Legion : http://masseffect.wikia.com/wiki/Legion

You will also notice the set of colors is a bit different for the head, and that it is bigger, mostly depending on the parts I had available, but I am quite satisfied with the result. I hope you are too

With a quickly built Vindicator assault rifle

With an even cheaper Widow anti-material rifle. Notice the facial expressions : lids and turning 'torchlight eye'.
The head is articulated as well, but I added so many pipes and stuff I can only turn it one or two clicks sideways and upwards. I think the outer look, on a model of this type counts more than the articulations.

'Damn, our wallet ! We knew this Kasumi human was not reliable !'

Haven't you heard about the Quarian stringless bass guitars ??

In fact, the kneecaps, in terms of look and liberty of movement are just right, but they can't stand a lot of torque and the body is almost too heavy for the legs. I managed to have him stand on his feet for the other pictures, but otherwise I put it on a stand I build. I know it's not the most elegant place, but come on, take a look at a drawing manikin ;)